Solution polyaluminoxane compositions are condensation products generally prepared by the partial hydrolysis of an organic aluminum compound. They are known to be useful as co-catalysts that efficiently activate the transition metal compounds serving as primary catalysts in the producing of olefin polymers. Polymethylaluminoxane compositions in which trimethylaluminum is employed as a starting material organic aluminum compound are widely known to perform particularly well as co-catalysts. These compositions are normally handled in the form of solutions obtained by dissolution in aromatic hydrocarbon solvents such as toluene.
Polymethylaluminoxane compositions perform well as co-catalysts. However, they are normally handled in a state where a primary catalyst such as a metallocene compound and polymethylaluminoxane composition have been dissolved in a solvent. Thus, the morphology of the polymer that is produced cannot be controlled. Not only does handling of the polymer present problems, but there is also a drawback in that fouling due to adhesion of the polymer to the polymerization reactor or the like occurs quite readily. Accordingly, use as is in slurry polymerization or vapor phase polymerization is problematic.
To solve these problems, a method of applying a supported solid polymethylaluminoxane composition—consisting of a polymethylaluminoxane composition supported on a solid inorganic support such as silica, alumina, or magnesium chloride—to suspension polymerization or vapor phase polymerization has been proposed. Silica is the most widely employed support among solid inorganic supports, and there are a number of examples of its use at the industrial level (see Patent References 1 to 5 and the like).
The above solid inorganic supports, including silica, are known to compromise the performance of polymers by tending to remain on the polymer, causing fisheyes, and the like. Solid polymethylaluminoxane compositions in which such supports have been employed are known to exhibit a greater drop in activity than in the polymerization activity in homogeneous system polymerization. Accordingly, to solve these problems, to reduce the negative impact of the support on the polymer while retaining the merits of a promoter in the form of a polymethylaluminoxane composition in a solid state, there is a need to develop a highly active supported solid polymethylaluminoxane composition.
Further, in methods known thus far, the compounds that can be employed as solid supports are limited. Not just any solid substance can be employed as a support. Even silica, which is industrially employed, must be controlled to achieve a pore size, pore capacity, and quantity of surface hydroxyl groups suited to the objective.